SolarEdge, Israel based company has definitely sensationalized the PV inverter market with HD wave technology claiming to double the power density delivered compared to traditional pv-inverters. What is this technology? Did it exist previously? If it did, what stopped it from being commercialized? How will it revolutionize the inverter market? Endless number of questions have flooded the internet. This post is an answer to these questions in a nutshell.
Innovation
in field of power electronics has not been as fast as in other fields. As a
result not much improvement in form factor and power density of inverters
have been observed in past few decades. The major challenge faced in this field
is the requirement of large magnetic components for filtering harmonics and large heat-sinks.
HD
wave technology has made a major breakthrough in existing technologies for PV
inverters nearly slashing the components size to half for the same output. It
uses distributed switching at high frequency to
produce multilevel voltage output producing a close to clean sine wave output. Major
difference between traditional and HD wave technology has been summarized in
the table below.
Let
us try to figure out how is it able to achieve it. Using distributed switching
multilevel output reduces the stress across the switches. This gives us an option
to replace high voltage, low frequency IGBTS with low voltage high frequency
MOSFETS. This prevents any need of high cost SiC and GaN to achieve the same output.
Equipped with powerful processing to synthesize close to clean sine wave output
and efficient switching coordination reduced the heat-sink requirement. As a
result the requirement of magnetic components
for filtering is reduced so is the heat-sink thus doubling the power density.
One Major
question arises - multilevel topology was first proposed in 1975 R. H. Baker
and L. H. Bannister and MOSFETS have been there since 1959. There have been several research
paper in past decade on multilevel topology. What kept it away for so long from
coming to market?
Well,
multilevel technology is already in use but only at high power level. At lower power
level, they do not offer as much economic viability as traditional inverter. The
cost of extra switches, isolated gate driver circuit for each of them,
capacitors exceed the cost saving by reducing the magnetic compound and heat-sinks. Also failure of switches has large impact on the quality of
waveform. There has to be a trade-off between redundancy and number of levels
of output voltage to mitigate the impact.
No
doubt, It's a bold move by solarEdge to bring multilevel inverter to lower
power level pv inverter. Market has high hopes from this technology as evident
from the revenue SEDGE made in fiscal year(144% increase). It has already shipped 920MW in fiscal year 2015. Cost effectiveness will be a major key to the success of this so
called breakthrough in PV inverter technology.
More information can be found in the links given below:
Things are getting smaller everyday. We would not be surprised to hear about nano-technology involving in power electronics in recent future... Nice post with timely information. All the best!
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